I got all 4 pandas with no dupes and 3 stones in the first 6 tries. I've done it twice since, and both times got a panda and a stone. So to me it seems a good drop rate, but that's probably just using all my luck up there so I can have 50,000 casts with no carp.

I've been holding this little tid bit for a while and now that i have dino fever had to share my CHEEEEEESE way to defeat ALL of these legendaries. It's all about quik damage and uber healing and nothing says that like the pet ability "Life Exchange" I believe this skill is limited to the Nether Faerie Dragon and the sprite darter(which i haven't lvled). I start with this pet and moon fire and takes some damage (remember the lower your health the bigger the averaging out of life is). Once at half life blamo 2k-2.9k damage. If up against a healing pet make sure to have some thing to get rid of the moon fire( such as darkness). Pending how much of a challenge I want to have depends on weather or not I kill of the Nether Faerie Dragon or put him back at full life for another cycle. Yes you can repeat this cheese wittling down these big SOBs till they are way under 1k....

There's actually a slightly cheesier way Before doing what you do, use a Terrible Turnip and its Sunlight skill, then the Life Swap does even more damage and you only have to whittle them down to 1500 ish. Once reached, use a Snowy Owl and Predatory Strike to finish.

Heh...I forgot i posted this a while back... due to my crazy drop rate i decided this would be a decent moneymaker. I've done the quest probably 10 more times. One panda and zero stones, guess my luck ran out.